The section that I've read is discussing the question of happiness from a philosophical point of view, and trying to examine whether possible future biotech therapies which would allow us to control our memories would be good for our happiness. It is an interesting question. They make some worthy arguments that the technology might not, in fact, bring about happiness, and that by implication it would not be good for society. But they begin the argument in this section with a discussion of the fundamental right to the pursuit of happiness, enshrined in the Declaration of Independence as the reason America exists. And therein lies the disconnect: they seem to be arguing, or at least laying the groundwork to argue, that the therapy would not be a good path to achieving happiness, and therefore people should not be allowed the option. But Jefferson never said we have the right to be happy. He said we have an unalienable right to pursue happiness -- not to actually achieve it. And my own reading of the meaning of that right is that it is fundamentally the right of each person to choose for himself how he wants to try to find happiness, and that includes ways that somebody else might not think were likely to actually lead to happiness.
The proper role of government enacting the principles of the Declaration is to maximize people's freedom to choose for themselves how to find happiness, not to seek to close off paths that people might choose to look down in their personal quests. People have to be free to make bad choices, or freedom is just an empty buzzword.